Textile fibers having soft hand characteristics and methods of making thereof

ABSTRACT

A fiber having a softer feel, which fiber comprises a fiber-forming polymer melt-blended with a bisamide additive is disclosed. A process of making the fiber having a softer feel formed by melt blending a fiber-forming polymer with a bisamide additive is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) fromprovisional U.S. patent application No. 60/721,448, filed on Sep. 28,2005.

BACKGROUND OF THE INVENTION

There is a need in the textile industry to develop and provide a fiberhaving a softer feel. Traditionally, fibers formed from various polymershave been treated post-extrusion with various spin finish compositions.However, the use of traditional topical spin finishes has not met theneed in the textile industry for the desired softer fibers. Somewax-based, topical spin finishes have resulted in softer fiber. However,these wax-based finishes have not been widely accepted or utilized bythe industry due to the housekeeping problems caused by thesolidification of wax on the machinery.

BRIEF SUMMARY OF THE INVENTION

By way of the present invention, it has now been surprisingly found thatthe above-described need in the textile industry can be advantageouslymet by providing a fiber having a softer feel, which fiber comprises afiber-forming polymer melt-blended with a bisamide additive.

More particularly, the fiber of the present invention comprises afiber-forming polymer melt-blended with a bisstearamide additive.

The fibers of the present invention advantageously possess a lower StickSlip measurement than a corresponding fiber, which was not treated withthe additive used in the present invention. The decrease in Stick Slipmeasurement of the fibers of the present invention is directlycorrelated to the softer feel of the fibers achieved by way of theinvention.

Another aspect of the present invention is a process of making the fiberof the present invention by melt blending a fiber-forming polymer with abisamide additive, preferably, a bisstearamide additive.

The fibers of the present invention have a wide variety of applicationsin the textile industry, particularly in those textile applicationswhere fibers having a softer feel are valued.

DETAILED DESCRIPTION OF THE INVENTION

Other than in the operating examples, or where otherwise indicated, allnumbers expressing quantities of ingredients or reaction conditions usedherein are to be understood as modified in all instances by the term“about.”

The present invention is directed to a fiber having a softer feel, whichfiber comprises a fiber-forming polymer melt-blended with a bisamideadditive of the formula:

wherein R and R″ can be the same or different and are straight orbranched alkyl groups having from 7 to 19 carbon atoms, R′ is a C₂-C₄linear alkyl group, preferably ethylene, and x is an integer of from 0to 5.

Preferred compounds of formula I are those having the formula:

in which R and R″ have the meanings described above. Particularlypreferred compounds of formula II are those containing at least one C₁₈acyl group (R═C₁₇), e.g., DETA bisstearamide (diethylenetriaminebisstearamide), DETA lauryl/stearyl amide and the like. Compounds inwhich R and R″ contain from 11 to 15 carbon atoms are also of interest,such as DETA bislaurylamide, DETA lauryl/palmityl amide and DETAbispalmitylamide, and the like.

The most preferred additive is N, N′-ethylene bisstearamide.

Fibers which can be formed by and the fiber-forming polymers which canbe used in the present invention include nylon, e.g., Nylon 6 and Nylon6,6, polyester, polypropylene, acrylic and the like. Any fiber formed byway of the present invention can advantageously achieve a desired softerfeel, as compared to the corresponding non-treated fiber.

Particularly preferred is fiber formed from polypropylene by way of thepresent invention based on the textile industry's desire to utilize apolypropylene fiber. Such fiber advantageously possesses the feel of anylon fiber. In addition, polypropylene is much cheaper than nylon. Soit is quite an advantageous accomplishment of the present invention toprovide a polypropylene fiber having the soft feel of nylon.

The fiber-forming polymer and additive of the present invention aremixed together and processed through an extruder. Typically, theextruder will operate at a temperature of from about 140 to about 220°C. during the extrusion process.

The amount of additive used in the fiber-forming process may range fromabout 0.25% to about 7% by weight, preferably from about 0.25% to about2% by weight.

The fiber denier may be varied from about 300/144 to about 1540/70.

Accordingly, the present invention advantageously provides the abilityto tailor the softness of the fiber by way of the combination of fiberdiameter and additive content. Furthermore, the additive mayadditionally provide benefits with respect to texturing bulkperformance.

In the fiber extrusion process carried out by way of the presentinvention, pellets of the polymer of interest are melted and conveyedthrough a heated extruder and then pumped through a spinneret to form asynthetic fiber. The bisamide additive, preferably a bisstearamide asdescribed above, can be added and blended with the polymer at the pointof extrusion. The additive can be metered as a concentrate into thethroat of the extruder at a rate to equal 1% distribution in the finalfiber. Alternatively, the additive can be blended with the polymerpellets from a 25% to 50% masterbatch at a ratio to result in a 1%distribution in the final fiber. The polymer with the additive blendedtherewith can then be processed through typical fiber extrusionconditions to achieve the fibers of the present invention.

The invention can be illustrated but not limited by the followingexamples.

EXAMPLES

DETA bisstearamide or N, N′-bisstearamide was blended with polypropylene(PP) resin at the point of extrusion. The blending step was completedeither by pre-blending the masterbatch by weight percent with the bulkpolymer in the hopper and mechanically mixing the two pellets or bymeter feeding the masterbatch pellets into the bulk polymer stream atthe throat of the extruder. The PP resin was varied from 14 MFI to 20MFI. The experiments were carried out over an additive range of 0.25% to7% by weight. The extrusion profile was 210, 215, 220, and 225° C. Thespin beam temperature was 255° C. The fiber denier range was varied from300/144 to 1540/70.

A relative ranking of the hand “feel” of the sample was made. A scale offrom 1 to 5 was used wherein a rating of 1 was equivalent to a very softhand and a rating of 5 was equivalent to a harsh, rough hand. The “Hand”or “feel” of the material was correlated to the Stick Slip (S/S)measurement of fiber friction.

Stick Slip behavior is observed in any sliding system in which thekinetic friction (F_(k)=force to maintain movement) is less than thestatic friction (F_(s)=force to begin movement). Surfaces will “stick”together until a sliding force of F_(s) is reached, then the surfaceswill “slip” over one another at the lower F_(k) value. This intermittentmotion will continually repeat itself at a constant sliding velocity.However, if the sliding velocity is continually increased, the systemwill eventually reach the point where F_(s)=F_(k) and stick slipbehavior will cease.

For the measurement in the Examples, the stick slip measurement wascompleted at a constant sliding velocity of 0.05 cm/min using apre-tension of 10% of the total yarn denier. The yarn was attenuatedaround a guide wheel and twisted around itself three times. The stickslip measurement was completed using a Rothschild Friction Meter andyarn take-up device. The friction meter contains the electronics used tomeasure the ingoing and outgoing tension. The take-up device provides aprecise yam path with tensiometer mounting positions, a guide wheel anda yarn winding wheel that assures constant yarn speed. The twotensiometers used to measure the ingoing and outgoing tension areessentially differential condensers. The tensiometer measuring headconsists of three prongs, the middle prong is the moveable measuringrod, which is mounted in a torsion spring that keeps it in a restposition. The two prongs on either side are screwed in yarn guides. Theyarn is inserted on top of the measuring rod and during operation therod is deflected by the moving yarn causing the capacity variations thatare transmitted to the friction meter and recorded.

As shown in the Table 1 below, when compared to the control with noadditive, the additive samples all exhibited a significantly lower S/Smeasurement. When the samples were felt, the samples of the presentinvention were readily identified as a much softer fiber with asignificantly lower S/S value, as compared with the control samples.TABLE 1 Denier Per Stick Slip S/S Hand F/M Friction F/F Friction StaticSample ID Filament cN 0.05 cm/min Rating cN 300 m/min cN 0.05 cm/minVolts Control 2 18 71 5 66 121 −16 *1973@1% 18 23 1 70 93 7 *1848@1% 1833 1 69 101 15 1433@1% 18 66 5 61 115 −10 1433@3% 18 54 4 67 108 −111433@5% 18 48 3 71 109 −12 1433@7% 18 24 1 73 86 −11 Control 22 53 5 58127 −112 **1973@0.25% 22 52 5 56 148 −171 **1973@0.375% 22 32 4 58 100−122 **1973@0.75% 22 36 4 58 124 −95 **1973@1.0% 22 36 3 57 111 −100**1973@1.5% 22 26 3 60 111 −42 Control tex. 2 10 5 22 26 227 *1973@3%tex. 2 2 1 23 25 151 *1973@5% tex. 2 4 2 23 20 1901433 flake allowed for adequate blending with the PP pellets allowing aloading of 1, 3, 5 and 7%. At 9% the 1433 caused screw slippage and wasnot further processed.*Standapol ™ F 1848, DETA bisstearamide, was provided in powder formfrom Cognis Brazil. The powder did not allow for adequate blending withthe PP pellets. Blended and Starve Fed by hand to control percentage at1 to 2%. At greater than 1.5% caused screw slippage.*CF 1973, N,N'-ethylene bisstearamide, was in the form of a small bead.The small bead did not allow for adequate blending with the PP pellets.Blended and Starve Fed by hand to control percentage at 1 to 2%. Atgreater than 1.5% caused screw slippage.**CF1973 in a 25% masterbatch of 20MFI PE. This masterbatch was blendedto give the final percentages in the yarn.Standapol ™ 1433 is a poly(alkyl vinyl ether), which can be obtainedfrom Cognis Corporation.

The results of the Examples clearly demonstrated that the additiveunexpectedly allowed for large denier per filament PP to advantageouslypossess the soft-hand feel of smaller denier PP and nylon fiber. Theadditive further advantageously and surprisingly did not cause anysignificant negative changes in the polypropylene fiber strengthcharacteristics.

1. A fiber having a softer feel which comprises a fiber-forming polymermelt-blended with a bisamide additive of the formula:

wherein R and R″ can be the same or different and are straight orbranched alkyl groups having from 7 to 19 carbon atoms, R′ is a C₂-C₄linear alkyl group, preferably ethylene, and x is an integer of from 0to
 5. 2. The fiber of claim 2 wherein the additive is N, N′-ethylenebisstearamide.
 3. The fiber of claim 1 wherein the additive is of theformula:

wherein said formula contains at least one C₁₈ acyl group (R═C₁₇). 4.The fiber of claim 3 wherein the additive is DETA bisstearamide.
 5. Thefiber of claim 3 wherein R and R″ of the additive formula contain from11 to 15 carbon atoms.
 6. The fiber of claim 1 wherein the fiber-formingpolymer is selected from the group of polymers consisting of nylon,polypropylene, polyester and acrylic.
 7. The fiber of claim 6 whereinthe fiber-forming polymer is polypropylene.
 8. The fiber of claim 1wherein the additive is present in an amount of from about 0.25% toabout 7% by weight.
 9. The fiber of claim 8 wherein the additive ispresent in an amount of from about 0.25% to about 2%.
 10. The fiber ofclaim 1, which fiber has a denier ranging from about 300/144 to about1540/70.
 11. A process of making a fiber having a softer feel, whichprocess comprises melt-blending a fiber-forming polymer with a bisamideadditive of the formula:

wherein R and R″ can be the same or different and are straight orbranched alkyl groups having from 7 to 19 carbon atoms, R′ is a C₂-C₄linear alkyl group, preferably ethylene, and x is an integer of from 0to 5.